6. Troubleshooting

The cursor appears as a white box, after switching modes

There is a known bug in the H/W cursor, that sometimes causes
the cursor to be redrawn as a white box, when the mode is changed.
This can be fixed by moving the cursor to a different region,
switching to the console and back again, or if it is too annoying
the H/W cursor can be disabled by removing the "HWcursor"
option.

The cursor hot-spot isn't at the same point as the cursor

With modes on the 6555x machines that are stretched to fill the
flat panel, the H/W cursor is not correspondingly stretched. This
is a small and long-standing bug in the current server. You can
avoid this by either using the "NoStretch" option or
removing the HWcursor" option.

The lower part of the screen is corrupted

Many DSTN screens use the top of video ram to implement a frame
accelerator. This reduces the amount of video ram available to
the modes. The server doesn't prevent the user from specifying
a mode that will use this memory, it prints a warning on the console.
The effect of this problem will be that the lower part of the screen
will reside in the same memory as the frame accelerator and will
therefore be corrupt. Try reducing the amount of memory consumed
by the mode.

There is a video signal, but the screen doesn't sync.

You are using a mode that your screen cannot handle. If it is a
non-standard mode, maybe you need to tweak the timings a bit. If
it is a standard mode and frequency that your screen should be
able to handle, try to find different timings for a similar mode
and frequency combination. For LCD modes, it is possible that your
LCD panel requires different panel timings at the text console than
with a graphics mode. In this case you will need the
"UseModeline" and perhaps also the "FixPanelSize"
options to reprogram the LCD panel timings to sensible values.

`Wavy' screen.

Horizontal waving or jittering of the whole screen, continuously
(independent from drawing operations). You are probably using a
dot clock that is too high (or too low); it is also possible that
there is interference with a close MCLK. Try a lower dot clock.
For CRT's you can also try to tweak the mode timings; try increasing
the second horizontal value somewhat.

Crash or hang after start-up (probably with a black screen).

Try the "NoAccel" or one of the XAA acceleration options
discussed above. Check that the BIOS settings are OK; in particular,
disable caching of 0xa0000-0xaffff. Disabling hidden DRAM refresh
may also help.

Hang as the first text is appearing on the screen on SVR4 machines.

This problem has been reported under UnixWare 1.x, but not tracked
down. It doesn't occur under UnixWare 2.x and only occurs on the
HiQV series of chips. It might affect some other SVR4 operating
systems as well. The workaround is to turn off the use of CPU to
screen acceleration with the
"XaaNoCPUToScreenColorExapndFill" option.

Crash, hang, or trash on the screen after a graphics operation.

This may be related to a bug in one of the accelerated
functions, or a problem with the BitBLT engine. Try the
"NoAccel" or one of the XAA acceleration options
discussed above. Also check the BIOS settings. It is also possible
that with a high dot clock and depth on a large screen there is
very little bandwidth left for using the BitBLT engine. Try
reducing the clock.

Chipset is not detected.

Try forcing the chipset to a type that is most similar to what
you have.

The screen is blank when starting X

One possible cause of this problem with older linux kernels is that
the "APM_DISPLAY_BLANK" option didn't work correct. Either upgrade
your kernel or rebuild it with the "APM_DISPLAY_BLANK" option
disabled. If the problem remains, or you aren't using linux, a
CRT/LCD or switch to and from the virtual console will often fix it.

Textmode is not properly restored

This has been reported on some configurations. Many laptops
use the programmable clock of the 6554x chips at the console.
It is not always possible to find out the setting that is
used for this clock if BIOS has written the MClk after the
VClk. Hence the server assumes a 25.175MHz clock at the
console. This is correct for most modes, but can cause some
problems. Usually this is fixed by switching between the LCD
and CRT. Alternatively the user can use the "TextClockFreq"
option described above to select a different clock for the
text console. Another possible cause of this problem is if
linux kernels are compiled with the "APM_DISPLAY_BLANK" option.
As mentioned before, try disabling this option.

I can't display 640x480 on my 800x600 LCD

The problem here is that the flat panel needs timings that
are related to the panel size, and not the mode size. There is
no facility in the current Xservers to specify these values,
and so the server attempts to read the panel size from the
chip. If the user has used the "UseModeline" or
"FixPanelSize" options the panel timings are derived
from the mode, which can be different than the panel size. Try
deleting theses options from XF86Config or using an LCD/CRT switch.

I can't get a 320x240 mode to occupy the whole 640x480 LCD

There is a bug in the 6554x's H/W cursor for modes that are
doubled vertically. The lower half of the screen is not accessible.
The servers solution to this problem is not to do doubling vertically.
Which results in the 320x240 mode only expanded to 640x360. If this
is a problem, a work around is to remove the "HWcursor"
option. The server will then allow the mode to occupy the whole
640x480 LCD.

After a suspend/resume my screen is messed up

During a suspend/resume, the BIOS controls what is read and
written back to the registers. If the screen is using a mode
that BIOS doesn't know about, then there is no guarantee that
it will be resumed correctly. For this reason a mode that is
as close to VESA like as possible should be selected. It is also
possible that the VGA palette can be affected by a suspend/resume.
Using an 8bpp, the colour will then be displayed incorrectly. This
shouldn't affect higher depths, and is fixable with a switch to
the virtual console and back.

The right hand edge of the mode isn't visible on the LCD

This is usually due to a problem with the "LcdCenter"
option. If this option is removed form XF86Config, then the problem
might go away. Alternatively the manufacturer could have incorrectly
programmed the panel size in the EGA console mode. The
"FixPanelSize" can be used to force the modeline values into
the panel size registers. Two machines that are known to have this
problem are the "HP OmniBook 5000" and the "NEC Versa
4080".

My TFT screen has a reddish tint in 24bpp mode

For 6554x chipsets the server assumes that the TFT bus width is
24bits. If this is not true then the screen will appear to have a
reddish tint. This can be fixed by using the "18BitBus"
option. Note that the reverse is also true. If the "18BitBus"
is used and the TFT bus width is 24bpp, then the screen will appear
reddish. Note that this option only has an effect on TFT screens.

SuperProbe won't work with my chipset

At least one non-PCI bus system with a HiQV chipset has been found to
require the "-no_bios" option for SuperProbe to correctly
detect the chipset with the factory default BIOS settings. The server
itself can correctly detect the chip in the same situation.

My 690xx machine lockups when using the "MMIO" option

The 690xx MMIO mode has been implemented entirely from the manual
as I don't have the hardware to test it on. At this point no testing
has been done and it is entirely possible that the "MMIO
option will lockup your machine. You have been warned! However if
you do try this option and are willing to debug it, I'd like to hear
from you.

My TrueColor windows are corrupted when using the "Overlay" option

Chips and Technologies specify that the memory clock used with the
multimedia engine running should be lower than that used without. As
use of the HiQV chipsets multimedia engine was supposed to be for
things like zoomed video overlays, its use was supposed to be
occasional and so most machines have their memory clock set to a value
that is too high for use with the "Overlay" option. So with
the "Overlay" option, using the "SetMClk" option to
reduce the speed of the memory clock is recommended.

The mpeg video playing with the XVideo extension has corrupted colours

The XVideo extension has only recently been added to the chips driver.
Some YUV to RGB colour have been noted at 15 and 16 bit colour depths.
However, 8 and 24 bit colour depths seem to work fine.

My ct69030 machine locks up when starting XFree

The ct69030 chipset introduced a new dual channel architecture. In its
current form, XFree can not take advantage of this second display
channel. In fact if the video BIOS on the machine sets the ct69030
to a dual channel mode by default, XFree will lockup hard at this
point. The solution is to use the BIOS setup to change to a single
display channel mode, ensuring that both the IOSS and MSS registers
are set to a single channel mode. Work is underway to fix this.

I can't start X-windows with 16, 24 or 32bpp

Firstly, is your machine capable of 16/24/32bpp with the mode
specified. Many LCD displays are incapable of using a 24bpp
mode. Also you need at least a 65540 to use 16/24bpp and at least a
65550 for 32bpp. The amount of memory used by the mode will be
doubled/tripled/quadrupled. The correct options to start the server
with these modes are

however as XFree86 version 4.0.3 allows 32bpp pixmaps to be
used with framebuffers operating in 24bpp, this mode of operating
will cost performance for no gain in functionality.

Note that the "-bpp" option has been removed
and replaced with a "-depth" and "-fbbpp"
option because of the confusion between the depth and number of
bits per pixel used to represent to framebuffer and the pixmaps
in the screens memory.

A general problem with the server that can manifested in many way such
as drawing errors, wavy screens, etc is related to the programmable
clock. Many potential programmable clock register setting are unstable.
However luckily there are many different clock register setting that
can give the same or very similar clocks. The clock code can be fooled
into giving a different and perhaps more stable clock by simply changing
the clock value slightly. For example 65.00MHz might be unstable while
65.10MHz is not. So for unexplained problems not addressed above, please
try to alter the clock you are using slightly, say in steps of 0.05MHz
and see if the problem goes away. Alternatively, using the
"UseVClk1" option with HiQV chips might also help.

For other screen drawing related problems, try the "NoAccel" or
one of the XAA acceleration options discussed above. A useful trick for
all laptop computers is to switch between LCD/CRT (usually with something
like Fn-F5), if the screen is having problems.

If you are having driver-related problems that are not addressed by this
document, or if you have found bugs in accelerated functions, you can
try contacting the XFree86 team (the current driver maintainer can be
reached at
dbateman@club-internet.fr
or
eich@xfree86.org
),
or post in the Usenet newsgroup "comp.windows.x.i386unix".